Lubricating metal surfaces during cold-working



Patented Mar. 21, 1939 LUBBICATING METAL SURFACES DURIN COLD-WORKING Norbert F. Toussaint, Pittsburgh, Pa., assignor to Gulf Research & Development Company,

Pittsburgh, Pa., acorporation of Pennsyl- Vania No Drawing. Application February 26, 193'], Serial No. 128,028

8 Claims. 11. 205-21) This invention relates to lubricating metal surfaces during cold-working; and it comprises in cold-working a metal subsequently to be annealed, a process improvement which resides in lubricat- 5 ing the surfaces of said metal by means of a lubricant comprising a petroleum lubricating .011 containing a minor amount, usually less than 5 per cent, of an oil-soluble oxygen-carrying or siccative metallic soap rendering said lubricant non-staining 'under annealing conditions, and sometimes improving the lubricating properties; all as more fully hereinafter set forth and as claimed.

Many metals are often worked cold. The metal,

such for example as aluminum, is fabricated into strips and sheets by cold-rolling operations in which the faces of the rolls are lubricated by petroleum lubricating oils, or compositions containing the same, such as a lubricant composed of 50 per cent kerosene, 48 per cent petroleum distillate of viscosity 200 S. U. V. at 100 F., and 2 per cent fish oil or other fatty vegetableor animal oil. Following fabrication by cold-rolling, the strip or sheet stock is ordinarily annealed.

25 Sheet stock is usually introduced into the annealing furnace in flat piles, while strip stock is commonly rolled into tight coils and then piled in the furnace. Thus, in the annealing operation, the surfaces of the sheet or strip are not well ex- 30 posed.

Annealing furnaces are often fired by gas bumers within the oven and the products of combustion come in contact with the metal. During annealing of rolled stock the temperature of the 35 metal is slowly raised until it reaches a peak temperature and the metal is then immediately allowed to cool. In one rolling mill the practice is to raise the temperature of the rolled stock to a peak of 900 F., after which the metal is imme- 40 diately allowed to cool. a

Owing, perhaps, to the restricted space adjacent the bulk of the metal surfaces and furthermore to the fact that conditions in the oven are not particularly conducive to good-combustion, 5 it has been found in the past that unless the residual oil film on the metal surface is removed prior to annealing, the oil is incompletely removed with practicable annealing temperatures. In such instances as the oil is not removed, stains 5 are left on the surface of. the annealed metal. Mineral oils, fish oils, etc., are cracked down by heat giving tarry or gummy residues and these contribute to the staining. Considerable cracking of the oils occurs at temperatures of 600-700 55 F. and higher.

Petroleum lubricating oils are also used in coldworking operations on metals other than rolling; for example, in drawingand stamping aluminum and in wire-drawing generally. In these operaao tions the lubricating oil prevents scoring or uneven drawing by allowing slippage between the' aluminum and the die. Whenever the aluminum being worked undergoes relatively high rubbing pressures or the changein shape of the stock is sufiicient, to leave residual strains, the drawn or stamped piece is ordinarily annealed at relatively mild temperatures. For instance, after one particular drawing operation, the drawn piece is annealed at temperatures between 600 F. and 650 F., these temperatures being maintained for about 5 hours, after which the metal is allowed to cool.

In the annealing of drawn or stamped aluminum, while the metal surface may be more exposed than in the annealing of sheet or strip stock, nevertheless the temperature of annealing is usually lower and oils heretofore considered suitable are more diificult to vaporize or burn; to get rid of without residue. Oils satisfactory for use in drawing operations include mineral oils of relatively high viscosity, such as residual lubricating oils having a viscosity of 5000 sec. S. U. V. at 100 F. Under the conditions encountered in the annealing furnace these heavy oils invariably leave stains of a gummy nature on the metal surfaces if not removed prior to annealing.

In the past, the elimination of stains produced as described has been accomplished by one of several alternatives. The residual lubricating oil film remaining on the metal after rolling, drawing, or stamping has been removed with a solvent before annealing or the stains produced have been removed chemically ormechanically after annealing. Either procedure introduces an expensive processing step. Recently, attempts have been made to solve the problem by the provision of water-oil emulsions to serve as lubricants in cold-working operations. Such emulsions are advantageous in that they may be removed from the metal surfaces by washing with water prior to annealing, but this step in itself complicates the working process and the known emulsions are disadvantageous in that they do not give proper lubrication under drawing conditions.

The provision of a method of lubricating metal surfaces properly during cold-working thereof which eliminates the necessity of processing to remove the residual film of lubricant before annealing, or of processing after annealing to remove stain produced by such lubricant, has

my invention, I lubricate the surfaces of the metal being worked by maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to deposit gum on and stain said metal surfaces during annealing thereof. and rendering said petroleum lubricating oil non-staining by incor-- porating therein an oil-soluble, oxygen carrying metallic soap known as a siccative in a small but sufliclent proportion substantially to retard the deposition of gum or stain when the metal is subsequently annealed. Most of these metal soaps facilitate the drying of linseed oil films with production of solid linoxyn by absorption of air oxygen and they are known as oxygencarriers; they are sold as siccatives. No drydrying of vegetable oils in paints and varnishes.

Among the heavy metal soaps which I find effective are the following: iron naphthenate, cobalt naphthenate, nickel naphthenate. copper naphthenate, manganese naphthenate, a mixture of cobalt, lead and manganese naphthenates,

lead naphthenates, lead oleate, a mixture of lead and cobalt naphthenates, mixed cobalt and zinc naphthenates, mired lead and manganese naphthenates, zinc naphthenate, chromium naphthenate, nickel palmitate and nickel stearate.

With the exception of the zinc soaps, the compounds I have found effective are all salts of' metals which exist in more than one state of oxidation. The naphthenates obtainable commercially vary in composition, since the naphthenic acids employed in their manufacture are mixtures of different acids. However, this variation in the composition of the naphthenates listed above does not appear to alter their efplace.

fectiveness. I

I employ these soaps in concentrations between of 1 per cent and 5 per cent by weight of the oil employed and in such proportions I find them to be soluble in petroleum oils.

- Under well understood principles, nickel naphthenate in a mineral oil tends to concentrate at the free face or the face next the metal in the case of lubricating oil. This rendersv more important the character of the surface layer of the oil than the restof it. And I have found that with oil containing a little nickel naphthenate, on cold rolling the metal and subsequent heating, there is less tendency to staining I attribute this to the fact that the active material coming into actual contact with the metal is largely the nickel naphthenate. I have found indeed that with a composition containing nickel naphthenate the actual viscosity of the carrypends on the type of oil employed, its viscosity,

and the conditions under which annealing takes The amount to be added is best deter- -mined empirically for any, particular operation.

In general, howeverfwith oils of relatively high viscosity I find it advantageous to incorporate more soap than with oils of lower viscosity. when the temperature reached during annealing is relatively high, I find it expedient to diminish the proportion-of soap added relative to that added when the metal is annealed at lower temperatures. Coastal oils appear to require less amounts of metal soaps than do Pennsylvania or Mid-Continent oils.

With oils of relatively low viscosity usually not more than 2 per cent by weight of a metal soap is required to effect the purpose of the invention. Such. small proportions are insufiicient to materially increase the viscosity of the lubricating oil. With oils of relatively high viscosity it is advantageous to incorporate more soap than with oils of lower viscosity, but the effect on viscosity is still insignificant, that is to say, while the addition of ,5nper cent of a metal soap might materially increase the viscosity of an oil normally having a viscosity of 1008. U. V. at 100 F., the same is not true when such a proportion is added to an oil of, say, 3400 S. U. V. at 1003 F.

In one actual embodiment of the invention, I formed a lubricating composition by incorporating 2 parts by weight of a commercial nickel naphthenate soap with 88 parts by weight of a solvent-refined Midi-Continent neutral distillate having a viscosity of 200 S. U. V. at 100" F.,.and 12 parts by weight lard oil. The mixture was then warmed to about 180 F. and stirred until homogeneous. This lubricant was tested by first applyingit in a thin film to both sides of several sheet aluminum discs. Each disc was then formed into a cylindrical shell by a drawing operation between the faces of diemembers; After drawing, the shells were stacked in an annealing furnace (according to known practice) and heated to a peak temperature of about 650 F., before being permitted to cool. After this treatment no visible traces of oil, gum or stain were left on. 4

the aluminum surfaces; the surfaces were bright. Comparative tests in which the aluminum ing 5 parts by weight of nickel naphthenate with Y parts by weight of a Pennsylvania 'residual j lubricating oil having a viscosity of 3400 S. U. V.

discs were coated with a thin film of a lubricant at F. The mixture was warmedand stirred until homogeneous. f The lubricant was tested in comparison with a lubricant consisting of' the same petroleum oil without the addition of metal soap, in amanner similar tothat described above. After annealing, the annealed shells which had.

been lubricated with my lubricant containing nickel naphthenate showed no visible traces of 011, gum, or stain and were clean and bright.

In comparison, those shells which had been lubricated with the petroleum oil alone were badly stained on withdrawal from the annealing furnace. v

' As the incorporation in petroleum lubricating oil of nickel naphthenate, copper naphthenate or other metallic soaps in accordance with my invention does not render the oil more volatile, it is somewhat difficult to explain the advantageous result attained thereby; and I content myself with noting the results. Suiiice it to say that when oil without the metal soap addition is present on the metal surfaces during annealing,

is deposited, but when the metal soaps according to my invention are incorporated in the lubricant, no such deposition takes place in the annealing treatment.

Gums are .usually complex, high molecular weight, oxygen-containingcompounds. They are products of incomplete oxidation. Perhaps the soaps I employ accelerate oxidation of the oil to a stage of complete combustion under annealing conditions. In any event, the result is significant.

An especially advantageous and unexpected .result which is incidentally effected by following the present invention is that in drawing operations or the like where high rubbing pressures are encountered, an oil of very low viscosity can now be satisfactorily employed when it contains any one of the soaps according 'to my invention. In one drawing operation it has heretofore been considered necessary to employ a petroleummil having a viscosity of 5000 S. U. V. at 100 F. in order to maintain satisfactory lubrication in preventing scoring of the metal and unevenness of drawing. I have found that the identical operatioh may be satisfactorily performed using as a lubricant a Mid-Continent solvent processed oil having a viscosity of 200 S. U. V. at 100 F. when such oil contains approximately 2 per cent by weight of nickel naphthenate or another of the metal soaps herein mentioned. The metal is not scored or unevenly drawn.

I have made comparative laboratory tests on various lubricating oils alone and the same oils containing the metal soaps as directed. In these tests, the oils employed were those used in various rolling, drawing and stamping operations. To simulate actual operating conditions, the aluminum metal was coated with a thin film of the sample to be tested and heated in a gas heated furnace for 4 hours at a temperature of 600 F., this being thetemperature of the metal as determined by a thermocouple. In each instance the lubricant without soap 4 addition left bad stains on the aluminum surface, while the identical lubricant containing between of 1 per cent and 5 per cent by weight of metal soap as described, left the alumiuum' surfaces bright and clean;

Among the compositions which I have so tested and found to be eflective are those .made up as follows: 7

Viscosit Compound in- Percent corporated b pie Base oil y weight Pb-Co naphthenate.

Ni naphthenate Ni naphthenate- Co naphthenate- P g-Co naphhenate HON- Solvent processed coast 0 naph- Zn nap thenate.

Ni naphthenate- Ni palmitate Ni stearate Pb naphthenate. Ni naphthenate. Cunaphthenate.

assess es s s see a s 0 Mid-Continent solvent processed.

While the invention has been described in its relation to the working of aluminum metal in particular, my method of lubrication is advantageous when applied to any metal being coldworked and subsequently to be annealed as it obviates the expensive step heretofore necessary to overcome staining and gum deposition, while affording proper lubrication of the metal surfaces.

For instance I have found my method advantageous in the cold-rolling of a stainless steel of the 18 per cent chromium 8 per cent nickel type. In one such operation, wherein the metal was rolled into sheets, I lubricated the faces of the rolls with a lubricating composition containing 98 parts by weight of a Pennsylvania neutral oil having 'a viscosity of 100 S. U. V. at 100 F. and two parts by weight nickel naphthenate. After the rolling operation the sheets were, without further treatment, annealed and on withdrawal from the annealing furnace the metal surfaces were bright and unstained. In comparison, when applicable to cold-working operations on nonferrous metals other than aluminum, such, for example, as Monel metal, particularly when such metals are to be annealed after cold-working, and where it is desirable that the surfaces be bright and clean after annealing.

Metal soaps of thetypes found useful in this invention are on the market as siccatives", as they promote the drying of linseed oil by oxygen carrying. While no fsiccative action is involved in the present invention, in thesense of converting a mineral oil to something like a dried varnish film, the name is convenient and may be here used. It is probable that the oxygen carrying power of the siccatives comes into play in the final removal of the grease from the metal by high temperature annealing. The removal is effected, at least in part, by air action there,-- that is, by oxidation.

What I claim is:

1. In cold-working a metal subsequently to be annealed, the improvement which comprises lubricating the surfaces of the metal being worked by' establishing and maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to deposit gum on and stain said metal surfaces during annealing thereof and rendering said petroleum lubricating oil non-staining by incorporating therein an oilsoluble metallic soap slccative in a small but suflicient proportion substantially to retard the deposition of gum under annealing conditions.

' 2. In cold-working metals subsequently. to be heat-treated at temperatures of 600 F. and upwards, the improvement which comprises lubricating the surfaces of the metal being worked by establishing and maintaining thereon a film of lubricant comprising a petroleum lubricating oil which would normally tend to deposit gum on and stain said metal surfaces during said heat treatment and rendering said petroleum lubricating oil non-staining by incorporating therein an oilsoluble metallic soap siccative in a small but sufficient proportion substantially to retard the deposition of gum at temperatures of 600 F. and upwards.

3. The method of claim 2 wherein said oilsoluble metallic soap is nickel naphthenate.

4. In cold-working aluminum subsequently tobe annealed, the improvement which comprises 'lubricating the surfaces of the aluminum being .worked by establishing and maintaining thereon 5 a film of lubricant comprising a petroleum lubricating oil which would normally tend to deposit gum on and stain said aluminum surfaces during annealing and rendering said petroleum lubricating oil non-staining by incorporating therein an oil-soluble metallic soap siccative in a small but suificient proportion substantially to retard the deposition of gum under annealing conditions.

5. A method according to claim 4, wherein said oil-soluble metallic soap is an oil soluble nickel 15 soap.

6. A method according to claim 4',wherein said oil-soluble metallic soap siccative is nickel naphthenate.

NORBERT F. TOUSSAINT. 

